One of the VERY best assuming the carb is correct for the engine and in good shape!!!!!
Total Vacuum controlled spark advance using a low venturi signal to advance spark.
Incorrect carb or vacuum signal= no or incorrect advance !!
The 1949-1953 Ford Loadamatic is a wonderfull distributor when used (in good shape) on a stock single carb engine.
The distributor is a vacuum advance only ( no mechanical advance) and works very well with a balanced synced vacuum supply.
The addition of a high lift camshaft and multiple carbs make this much needed vacuum signal imposible to tune. Making the engine have little control on spark advance. ( a mechanical advance aftermarket unit is needed ).
See our Delco Conversion page above pg 1 &2..
Cast and aluminum loadamatic units are used based on engine and cover styles . Cast iron with a cast front cover and aluminum with the aluminum cover.
Cast and Merc with lower support are shown.
These units are somewhat difficult to rebuild as they need to be totally torn down to verify good bushings and connection wire under the plate.
Plate moves with vacuum change and lead wire can become shorted.
Also the drive gear is a very tight press-fit requiring heat and a drill press to remove gear. We typically replace gear and vacuum can on a rebuild.
Spark advance rate is adjusted by turning the two spring posts ( eccentric pin) making the springs tighter or looser based on need to get within factory specification.
Small spring is light vacuum and larger spring is for higher vacuum. This is measured carb venturi vacuum advance , not actual manifold!